Questions: A. Actin B. Collagen C. Intermediate filaments D. Microtubules

Solution Steps

The yellow arrows point to fibrous structures within Cell A. These structures appear to be long, thin, and thread-like.

A. Actin is a globular protein that forms microfilaments. While involved in cell structure, it doesn't typically appear as long, distinct fibers in electron micrographs like this. B. Collagen is a major component of the extracellular matrix (ECM). It is typically found outside of cells. While the image shows two cells next to each other, the arrows clearly point to intracellular structures, not ECM. C. Intermediate filaments are rope-like fibrous proteins that provide structural support within the cell's cytoplasm. Their appearance in electron micrographs aligns with the structures indicated by the arrows. D. Microtubules are hollow cylindrical structures involved in intracellular transport and cell division. They are typically straighter and more tube-like than the structures indicated.

Final Answer C. Intermediate filaments